Different coupling mechanisms for a novel modular plate in acetabular fractures-a comparison using a laparoscopic model.

Introduction: Acetabular fractures are among the most challenging injuries in traumatology. The complex anatomy usually requires extensive surgical approaches baring the risk for iatrogenic damage to surrounding neurovascular structures. As a viable alternative, minimally invasive endoscopic techniques have emerged during the recent years. This paper reports on the feasibility of different coupling mechanisms for a novel suprapectineal plate especially designed for minimally invasive acetabular surgery. Methods: A total number of 34 participants contributed to the present study, who differed in their arthroscopic and surgical experience. A laparoscopic model was used to compare four different coupling mechanisms by the number of failed attempts, the time required for plate fixation, the influence of surgical experience as well as the learning success for each individual coupling mechanism. Moreover, the feasibility of each mechanism was evaluated by a questionnaire. Results: The results demonstrate that plates employing grooved and pressure-sliding coupling mechanisms exhibit fewer failed attempts and reduce trial times, especially in contrast to sole sliding mechanisms. Furthermore, our study revealed that proficiency in endoscopic procedures significantly influenced the outcome. Notably, the subjective evaluation of the participants show that the pressure base and pressure-slide base plate designs are the most supportive and feasible designs. Conclusions: In summary, the present study evaluates for the first-time different plate and coupling designs for minimal-invasive surgery, indicating a superior feasibility for plates with a grooved and pressure-sliding mechanism.

[Cement augmentation in pelvic ring fractures]. / Zementaugmentation bei Beckenringfrakturen.

Cement augmentation of sacroiliac (SI) screws in the posterior pelvic ring has been shown to provide greater biomechanical stability in cadaveric studies. Pelvic ring fractures are relatively rare compared to the total number of fractures. Nevertheless, the 1­year mortality rate of up to 27% is very high, especially for geriatric pelvic ring fractures and is also largely associated with reduced mobility due to the fracture. The primary goal of treatment is therefore the restoration of patient mobility. This requires the achievement of sufficient stability of the pelvic ring. As osteoporosis is often a causative factor for the pelvic ring fracture, a more stable anchoring of the implants in the osteoporotic bone can be achieved by cement augmentation. This article presents the possibilities of cement augmentation of the pelvic ring and describes the technique of cement-augmented SI screws.

Gold(I) and mercury(II)-isoelectronic ions with strongly different chemistry: ab initio QMCF molecular dynamics simulations of their hydration structure.

The hydration structure of the isoelectronic Au(I) and Hg(II) ions was determined by means of ab initio quantum mechanical charge field molecular dynamics (QMCF MD) simulations. The two hydrates proved as very labile but entirely different in their structural features. While Hg(II) forms two distinct hydration shells, Au(I) is characterized by an additional extended first shell (meso-shell) which has a considerable influence on all data extracted from the simulation trajectory, namely, radial and angular distribution functions, coordination number distribution, and dynamical data such as mean ligand residence times (MRT) and vibrational frequencies. The short MRT values of the first shell ligands, amounting to a few picoseconds, lead to the simultaneous presence of a number of hydrate complexes with differing geometries, which explains the difficulties in assigning structural data to spectroscopic measurements. The results presented here demonstrate that isoelectronic transition metal ions can show strongly different chemical properties, which cannot be explained on the basis of their different charge alone. The importance of including the second hydration shell and thus the intershell hydrogen bonds in the quantum mechanical treatment of the simulation is clearly proven.

Temperature dependence of structure and dynamics of the hydrated Ca2+ ion according to ab initio quantum mechanical charge field and classical molecular dynamics.

Simulations using ab initio quantum mechanical charge field molecular dynamics (QMCF MD) and classical molecular dynamics using two-body and three-body potentials were performed to investigate the hydration of the Ca(2+) ion at different temperatures. Results from the simulations demonstrate significant effects of temperature on solution dynamics and the corresponding composition and structure of hydrated Ca(2+). Substantial increase in ligand exchange events was observed in going from 273.15 K to 368.15 K, resulting in a redistribution of coordination numbers to lower values. The effect of temperature is also visible in a red-shift of the ion-oxygen stretching frequencies, reflecting weakened ligand binding. Even the moderate increase from ambient to body temperature leads to significant changes in the properties of Ca(2+) in aqueous environment.